The present invention relates to an idling speed control device of an internal combustion engine.
In order to control the number of revolutions per minute of an engine so that it becomes equal to a predetermined number when the engine is idling, the applicant has proposed an idling speed control device in which a bypass passage branches off from the intake passage of the engine, which is located upstream of a throttle value, and connected again to the intake passage located downstream of the throttle valve, with a flow control valve device being arranged in the bypass passage. The flow control valve device is driven by a stepper motor for controlling the amount of air flowing within the bypass passage at the time of idling. In this idling speed control device, the flow control valve device comprises a valve chamber having an air inlet opening and an air outlet opening, and the amount of air flowing within the bypass passage is controlled in such a way that the flow area of the air outlet opening of the valve chamber is changed by a control valve which is driven by the stepper motor. However, since the air flowing within the bypass passage contains water vapor therein, when the flow control valve device is used for a long time, water gradually accumulates in the valve chamber. As a result of this, in a cold season since the water accumulated in the valve chamber is frozen, the control valve freezes to the housing of the flow control valve device and, thus, there is the possibility that the control valve cannot move.